The invention relates to the rapping of discharge and field electrodes in a high voltage driven electrostatic precipitator for the cleansing of smoke laden gases from industrial plants, power works etc. Such rapping is necessitated by the fact that due to the mode of operation of the precipitator dust will settle on the electrodes and has therefore, at intervals, to be removed from same by transferring an impact force to the electrodes so that these are subjected to a forceful vibration by which the deposited dust is loosened.
The necessary impact force for the rapping of the electrodes is usually obtained by a number of hammers fixed to a rotary shaft which spans the width of the precipitator, and which are lifted upwards from a vertical pendent position in order to be released so that they fall back towards their vertical position. For each individual hammer a bar or a lever is rapped by the hammer when it falls back, the bar/lever transferring the supplied impact energy to a section of precipitator electrodes.
Whether the hammers, as it is known from the rapping mechanism according to U.S. Pat. No. 3,844,742, are moved 360 degrees about their suspension shaft, or as described in GB No. 2 138 710 are moved ony 180 degrees at the most, such a rapping mechanism requires quite a lot of space at the bottom of the precipitator sections or above these, as the length and/or height of the house enclosing the precipitator has to be enlarged accordingly, resulting in an additional consumption of materials and space.
Furthermore, the bearings from which the hammers are suspended and rotating and the bearings which support the rotary shaft operate in highly dust-laden surroundings, which involves hard wear.
Another known mechanism for the rapping of electrodes is shown in DE-PS No. 370 148 according to which the released energy from the impact of a freely falling ball against an electrode or its carrying frame is utilized for the rapping whereafter the ball is led back by a lifting device to its starting position before the rapping. The advantage of this mechanism is that in a very simple way it solves some of the existing insulation problems of an electrostatic precipitator in avoiding undesirable sparkovers between the electrodes and the applied rapping mechanism. On the other hand it presupposes that each individual electrode suspension has a separate mechanism with its own ball and lifting device which, especially in larger electrostatic precipitators with many carrying frames, will involve a very complicated apparatus with many mobile parts.
It is therefore the object of the invention to provide a rapping mechanism to avoid the drawbacks of the above known mechanisms.